Conventional filled polymer composites are polymers filled with inorganic fillers (e.g., talc and calcium carbonate) that essentially act as economic fillers usually without improving physical or mechanical properties of the polymers. Nanocomposites comprised of polymers and clays (e.g., natural clays or synthetic organoclays) have been investigated, but these conventional clay nanocomposites are typically prepared by contacting together the polymers and either dry clay powders or an organic solvent-wet clay. Conventional clay nanocomposites wherein the polymer is hydrophobic usually contain clays that are poorly exfoliated (i.e., clays lacking dimensions less than 100 nanometers) and frequently agglomerated. Mechanical properties of such composites typically offer no or only minor improvement over mechanical properties of conventional filled polymers. Further, preparing such nanocomposites using methods that employ an organic solvent-wet clay lack sufficient safety and environmental benefits due to the flammability, explosiveness, toxicity, and waste treatment problems associated with the organic solvent.
Hasegawa N., et al. mention preparing a polymer nanocomposite from an inorganic clay, sodium montmorillonite (NaMMT), and the polymer, nylon-6, by compounding a water slurry of NaMMT with a melt of nylon-6 in an extruder (Hasegawa N., et al., Polymer, 2003;44(10):2933-2937).
Using a different method, Zhong-Zhen Y., et al. mention preparing another polymer nanocomposite from NaMMT and nylon-6, by compounding a powder of the NaMMT with a melt of nylon-6 in an extruder receiving a downstream injection of water (Zhong-Zhen Y., et al., Journal of Polymer Sci. Part B: Polymer Physics, 2005;43(9):1100-1112). Zhong-Zhen Y., et al. also mention preparing a composite from a melt of nylon-6 and a powder of an organoclay, OMMT—obtained by ion exchange of NaMMT with dioctadecyldimethylammonium cation—in an extruder receiving a downstream injection of water, but Zhong-Zhen Y., et al. also mention that this preparation did not favor exfoliation and dispersion of the organoclay. Zhong-Zhen Y., et al. also mention that adding water during melt compounding had little influence on mechanical properties of the resulting nylon-6/OMMT polymer nanocomposite compared to mechanical properties of a nylon-6/OMMT polymer nanocomposite prepared by an analogous process lacking injection of water.
European Patent Number EP 0 398 551 B1 mentions kneading nylon-6 with a dispersion medium and a water-wet organoclay, 12MMT, in an extruder. The 12MMT was obtained by exchanging more than 100% of an ion exchange capacity of a NaMMT with excess aqueous 12-ammoniumdodecanoic acid cations. In the process of EP 0 398 551 B1, a dispersion medium is required. For instance, Example 5 mentions using a 1:9 mixture of the 12MMT:water. Further, EP 0 398 551 B1 teaches that a minimum amount of the dispersion medium is necessary. For instance, Example 1 mentions successfully using a 1:9:9 mixture of 12MMT:water:ε-caprolactam. Comparative Example 5 mentions that using less dispersion medium, particularly using a 1:0.25:0.25 mixture of 12MMT:water:ε-caprolactam (i.e., the dispersion medium comprising 0.5 parts of a dispersion medium of 1:1 water:ε-caprolactam), fails to give product.
Sun L., et al., Preparation of Exfoliated Epoxy/α-Zirconium Phosphate Nanocomposites Containing High Aspect Ratio Nanoplatelets, Chem. Mater., 2007;19:1749-1754 mention an epoxy polymer nanocomposite comprising D.E.R. 332 epoxy resin (The Dow Chemical Company) cured with 4,4′-diaminodiphenyl sulfone and an organosalt comprising alpha-zirconium phosphate. The epoxy polymer nanocomposite is prepared by combining a mixture of the organosalt and acetone with the D.E.R. 332 epoxy monomer, sonicating, removing the acetone to give a dispersion of the organosalt in the monomer, adding the 4,4′-diaminodiphenyl sulfone, and curing the resulting mixture.
Polymer nanocomposites comprised of highly exfoliated organoclay or organosalt (i.e., organoclay or organosalt that is partially or fully delaminated such that at least 50% of particles thereof have at least one dimension that is less than 100 nanometers) and methods of preparing such polymer nanocomposites are needed. Compared to conventional filled polymer composites and conventional organoclay or organosalt nanocomposites, such polymer nanocomposites may provide one or more improved mechanical properties such as, for example, increased modulus (e.g., flexural modulus), lower density, improved optical clarity, lower coefficient of thermal expansion, in some instances increased impact toughness, or a combination thereof.